Milk fat and primary fractions obtained by dry fractionation

Dry fractionation efficiency of milk fats from different sources and the characteristics of their fractions in chemical composition, thermal property, and crystal morphology

The physicochemical properties of anhydrous milk fats (AMF) often change according to different regions and seasons, inevitably affecting dry fractionation. This study analyzed the differences in the fraction yields and physicochemical characteristics of four AMFs from different sources. The results showed that single-stage dry fractionation conducted at 25 °C easily separated AMFs into liquid fractions (L25) and solid fractions (S25) via pressure filtration, both producing satisfactory yields. Moreover, all L25s exhibited few crystals with good fluidity at 25 °C, while S25s presented as semi-solids supported by β crystal networks with a certain hardness and plasticity. However, four AMFs displayed fractionation efficiency variation, while the thermal differences among them showed no obvious correlation with those among their fractions. Generally, more trisaturated triglycerides with 48 to 54 carbon atoms in the AMF increased the S25 yield and decreased the slip melting points (SMP) of both fractions.

Fatty acid, triglyceride, and kinetic properties of milk fat fractions made by the combination of dry fractionation and short-path molecular distillation

In this study, we aimed to detect the physicochemical properties of distilled products (residue and distillate) obtained from anhydrous milk fat (AMF) and its dry fractionation products (liquid and solid fractions at 25°C [25 L and 25 S]). The results showed that the saturated fatty acids and low- and medium molecular-weight triglycerides were easily accumulated in the distillate, and the percentage of unsaturated fatty acid and high molecular-weight triglycerides in the residue were higher, and these components in 25 S and 25 L were influenced more significantly than those in the AMF. In addition, the distillate had larger melting ranges in comparison with the distilled substrate, while the melting ranges of residue was smaller. The triglycerides were presented as the mixture crystal forms (α, β', and β crystal) in 25 S, AMF, and their distilling products, and it was transformed gradually to a single form as the increasing of distilling temperature. Moreover, the accumulated pattern of triglycerides was double chain length in 25 S, AMF, and their distilling products. These results provide a new approach to obtain the milk fat fractions with different properties, and the findings of this study enrich the theoretical basis of milk fat separation in practical production.

Polymorphism of a Highly Asymmetrical Triacylglycerol in Milk Fat: 1-Butyryl 2-Stearoyl 3-Palmitoyl-glycerol

Milk fat has more than 200 triacylglycerols (TAGs), which play a pivotal role in its crystallization behavior. Asymmetrical TAGs containing short butyryl chains contribute to a significant portion of milk fat TAGs. This work aims to elucidate the crystallization behavior of asymmetrical milk fat TAGs by employing the pure compound of 1-butyryl 2-stearoyl 3-palmitoyl-glycerol (BuSP). The structural evolution of BuSP after being cooled down to 20 °C from the melt is evaluated by small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC). The temporal structural observation shows that BuSP crystallizes into the α-form with short and long spacings of 4.10 and 56.9 Å, respectively, during the first hour of isothermal hold at 20 °C. The polymorphic transformation of the α to β' phase occurred after 4 h of isothermal hold, and the β'- to α-form fraction ratio was about 70:30 at the end of the isothermal experiment (18 h). Pure β'-form X-ray patterns are obtained from the BuSP powder with short spacings of 4.33, 4.14, and 3.80 Å, while the long spacing of 51.2 Å depicts a three-chain-length lamellar structure with a tilt angle of 32°. Corresponding DSC measurements display that BuSP crystallizes from the melt at 29.1 °C, whereas the melting of α- and β'-forms was recorded at 30.3 and 47.8 °C, respectively. In the absence of the β-form, the β'-polymorph is the most stable observed form in BuSP. This work exemplarily explains the crystallization behavior of asymmetrical milk fat TAGs and thus provides new insights into their role in overall milk fat crystallization.

Structural Mechanism and Hydrolysis Kinetics of In Vitro Digestion Are Affected by a High-Melting-Temperature Solid Triacylglycerol Fraction in Bovine Milk Fat

High-melting-temperature solid triacylglycerol (TAG) is the main source of controversy with regard to the nutritional assessment of milk fat. This study investigated the microscopic changes and hydrolysis kinetics of milk fat globules (MFGs) reconstituted with butterfat and its primary fractions (30S, 20S, and 20L) during in vitro digestion. The 30S, 20S, and 20L on behalf of high-, medium- and low-melting-temperature fractions, respectively, had well-distinguished melting temperatures (42.1, 38.9, and 22.0 °C) and long-chain saturated TAG contents (19.3, 3.2, and 1.8%). The results revealed that the gastrointestinal fate of these butterfat fractions varied greatly with their TAG composition, and the gastric phase was a sensitive target in terms of the physiological site. The 20S- and 30S-reconstituted MFG emulsions during gastric digestion compared to that of 20L had higher extensive aggregation, lower hydrolysis extent (29.8, 28.0, and 57.3%, respectively), and slower apparent hydrolysis rate constants k (2.4, 2.1, and 6.1 min^-1, respectively).

New insights into the digestion and bioavailability of a high-melting-temperature solid triacylglycerol fraction in bovine milk fat

Clarifying the health risks associated with the consumption of high-melting-temperature solid triacylglycerol (TAG) from milk fat has profound significance for the nutritional evaluation and development of new dairy products. Our previous work effectively separated butterfat into solid/liquid fractions (30S and 30L) at 30 °C and successfully reconstituted milk fat globules (MFGs) with these fractions. The current study examined the postprandial digestive and daily metabolic properties of a high-melting-temperature solid TAG fraction by performing animal experiments (rats) with 30S-reconstituted MFG emulsion gavage for 240 min and 30S-containing diet administration for 4 weeks. Compared to the consumption of whole butterfat, 30S consumption altered apolipoprotein levels and did not lead to dyslipidaemia in the rats. Conversely, 30S administration induced significant body weight loss by enhancing satiety signals (glucagon-like peptide 1, GLP-1; cholecystokinin, CCK; and peptide YY, PYY), increasing faecal losses, and upregulating the level of hepatic lipolysis-associated enzymes (hormone-sensitive lipase, HSL; adipose triglyceride lipase, ATGL; and protein kinase A, PKA). The 30S diet efficiently improved adipocyte hypertrophy and reduced fat accumulation by downregulating the level of acetyl-CoA carboxylase (ACC) in adipose tissue. This study is of relevance to nutrition science and the dairy industry.

Fat crystallization of blends of palm oil and anhydrous milk fat: A comparison between static and dynamic-crystallization

The application of dynamic-crystallization (a combination of shear with rapid cooling) often plays an important role in the production of industrial fat-based products such as shortenings/margarines but has been rarely reported. In this study, three blends of palm oil (PO) with anhydrous milk fat (AMF) (0, 25 and 50% AMF, w/w) were rapidly crystallized under static (using freezer) and dynamic conditions (using a benchtop scraped surface heat exchanger). Various techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized light microscopy (PLM), rheology and texture analysis were applied to investigate physicochemical properties of fat blends as well as their crystal morphology upon the long-term storage (4 weeks) at 5 °C and 15 °C. The results revealed that high cooling rate of dynamic-crystallization not only affected melting behavior of fat blends but also prevented the polymorphic transformation from β' to β crystals. Besides, the application of shear during fat crystallization helped to improve significantly the gel strength of produced shortenings. Although post-crystallization of low melting triacylglycerols (TAGs) occurred for all produced shortenings during storage at 5 °C which was accompanying with a firmness increase, it was more considerable for samples owning higher AMF content. Moreover, this phenomenon promoted the sintering as well as Ostwald ripening between fat crystals of dynamic-crystallized fat blends resulting in the formation of unwanted large aggregates (or granular crystals) with the size ranging from 100 to 500 μm.

A novel approach for the reconstitution of bovine milk fat globules with different-melting-temperature triacylglycerol cores

Reconstructing milk fat globules (MFG) with different-melting-temperature triacylglycerols (TAG) to improve its nutritional and functional properties has great potential for expanding industrial applications. Butterfat was fractionated by stepwise crystallization at 30, 20 and 15 °C to yield six fractions (30S, 30L, 20S, 20L, 15S and 15L). Fractions were analyzed for thermal properties and fatty acid composition. An efficient method for analyzing TAG was established using HPLC-ESI-Q-TOF-MS/MS combined with principal component analysis, and total 146 TAGs in butterfat and its fractions were identified. The melting enthalpy, melting temperature, and long-chain saturated TAG content of 30S fraction were 71.5 J/g, 42.1 °C, and 19.3%, respectively, while that of 15L fraction corresponded to 11.9 J/g, 17.1 °C and 0.1%, indicating that the butterfat was effectively separated. Then MFG were reconstituted with milk fat globule membrane and different-melting-temperature TAG cores from obtained fractions, and reconstituted MFG gave excellent microstructural stability and emulsifying activity.

Design of new lipids from bovine milk fat for baby nutrition

The lipid phase of infant formulas is generally composed of plant-based lipids structured with a high concentration of palmitic acid (C16:0) esterified at the sn-2 position of triacylglycerol since this structure favors the absorption and metabolism of fatty acids. Palm oil is commonly used to make up the lipid phase of infant formulas due to its high concentration of palmitic acid and solids profile and melting point similar to human milk fat. However, the addition of palm oil to infant formulas has been associated with the presence of 3-monochloropropane-1,2-diol (3-MCPD) esters, a group of glycerol-derived chemical contaminants (1,2,3-propanotriol), potentially toxic, formed during the refining process of vegetable oil. Bovine milk fat obtained from the complex biosynthesis in the mammary gland has potential as a technological alternative to replace palm oil and its fractions for the production of structured lipids to be used in infant formulas. Its application as a substitute is due to its composition and structure, which resembles breast milk fat, and essentially to the preferential distribution pattern of palmitic acids (C16:0) with approximately 85% distributed at the sn-1 and sn-2 position of triacylglycerol. This review will address the relationship between the chemical composition and structure of lipids in infant nutrition, as well as the potential of bovine milk fat as a basis for the production of structured lipids in substitution for the lipid phase of vegetable origin currently used in infant formulas.

Milk fat: opportunities, challenges and innovation

Milk fat is a high-value milk component that is processed mainly as butter, cheese, cream and whole milk powder. It is projected that approximately 35 million tonnes of milk fat will be produced globally by 2025. This surplus, enhances the need for diversification of milk fat products and the milk pool in general. Infant milk formula producers, for instance, have incorporated enzyme modified ("humanised") milk fat and fat globule phospholipids to better mimic human milk fat structures. Minor components like mono- and di-glycerides from milk fat are increasingly utilized as emulsifiers, replacing palm esters in premium-priced food products. This review examines the chemistry of milk fat and the technologies employed for its modification, fractionation and enrichment. Emerging processing technologies such as ultrasound, high pressure processing, supercritical fluid extraction and fractionation, can be employed to improve the nutritional and functional attributes of milk fat. The potential of recent developments in biological intervention, through dietary manipulation of milk fatty acid profiles in cattle also offers significant promise. Finally, this review provides evidence to help redress the imbalance in reported associations between milk fat consumption and human health, and elucidates the health benefits associated with consumption of milk fat and dairy products.

Milk fat crystal network as a strategy for delivering vegetable oils high in omega-9, -6, and -3 fatty acids

As an alternative to the strategies currently used to deliver unsaturated fatty acids, especially, the essentials omega-6 and 3- fatty acids, the aim of this work was to investigate the effect of the incorporation of 25 e 50% (w/w) of olive, corn and linseed oil into the crystal structure of anhydrous milk fat (AMF). Fatty acid composition, atherogenicity (AI), and thrombogenicity (TI) index, crystallization kinetics, polymorphism by Rietveld method (RM), microstructure, thermal behavior, solid fat content, and lipid compatibility was evaluated. The addition of vegetable oils reduced the saturated fatty acids, and the AI and TI indices of AMF, and increased the concentration of unsaturated, specifically omega-6 and -3 fatty acids. Although vegetable oils caused changes in nucleation and crystallization kinetics, the spherulitic and crystalline morphology and the β' polymorphism of AMF were maintained. The study demonstrated the possibility of using the crystal structure of AMF as a vehicle for unsaturated fatty acids in food formulations, as an alternative to nutritional supplementation. In addition, studies on the use of RM in blends made with AMF and vegetable oil have not been found in literature, thus demonstrating the relevance of the present study.

Effect of Fractionation and Chemical Characteristics on the Crystallization Behavior of Milk Fat

The experiments reported in this study provided a more comprehensive insight into the effect of chemical composition on the crystallization behavior of milk fat (MF). MF was fractionated between 20 and 40 °C into nine fractions with different melting points and was first subjected to the heating step (L20, L30, L40, and S40) followed by the cooling phase (SS40, SL40, SS30, SL30, and LL40). Furthermore, the species of fatty acids (FAs) and triglycerides (TAGs) of the MF fractions were identified. The thermodynamics, crystallization behavior, and polymorphs were determined using differential scanning calorimetry, pulsed nuclear magnetic resonance, and X-ray diffraction, respectively. The results indicated that L40 yielded the highest percentage (∼35% of the total MF) of all the fractions. Enthalpies of the melting and crystallization processes of solid fat content in this study were related to the different FA and TAG compositions of MF and its fractions. High melting fractions (HMFs) were enriched with long-chain saturated fatty acids and tri-saturated (S3) TAGs, and low melting fractions (LMFs) were enriched with short-chain unsaturated FAs and tri-unsaturated (U3) TAGs. Moreover, the various nucleation mechanisms of MF fractions were identified according to the Avrami equation. The polymorphic transformation from a β' form of double chain length structures to a β form of triple chain length occurred in the native MF and HMFs, whereas the LMFs displayed almost no crystals. PRACTICAL APPLICATION: This study represented the first time that nine fractions were obtained using MF fractionation via a heating step, followed by a cooling phase. Furthermore, the chemical composition of MF fractions was investigated. The results obtained from this study might be of specific value in understanding the functional properties of fat-based dairy food in both storage conditions and real-time applications.

Potential of Milk Fat to Structure Semisolid Lipidic Systems: A Review

Food production and consumption patterns have changed dramatically in recent decades. The universe of oils and fats, in particular, has been changed due to the negative impacts of trans fatty acids produced industrially through the partial hydrogenation of vegetable oils. Regulations prohibiting its use have led the industry to produce semisolid lipid systems using chemical methods for modification of oils and fats, with limitations from a technological point of view and a lack of knowledge about the metabolization of the modified fats in the body. Milk fat is obtained from the complex biosynthesis in the mammary gland and can be a technological alternative for the modulation of the crystallization processes of semi-solids lipid systems, once it is naturally plastic at the usual processing, storage, and consumption temperatures. The natural plasticity of milk fat is due to its heterogeneous chemical composition, which contains more than 400 different fatty acids that structure approximately 64 million triacylglycerols, with a preferred polymorphic habit in β', besides other physical properties. Therefore, milk fat differs from any lipid raw material found in nature. This review will address the relationship between the chemical behavior and physical properties of semisolid lipids, demonstrating the potential of milk fat as an alternative to the commonly used modification processes.

Characterisation of triacylglycerols from bovine milk fat fractions with MALDI-TOF-MS fragmentation

In this study, we used MALDI-TOF-MS to profile and characterise the triacylglycerol (TAG) species of anhydrous bovine milk fat (AMF) and its low melting (olein) and high melting (stearin) fractions obtained by dry fractionation. Silver-ion solid phase extraction (Ag⁺-SPE) cartridges were utilised to separate the TAGs according to saturation degree. Then, several TAG species were selected and fragmented via post-source decay (PSD) fragmentation. MALDI-TOF-MS TAG profiles and fragmentation patterns were compared to the TAG and fatty acid (FA) compositions obtained by gas chromatography-flame ionization detector (GC-FID). We found that, olein was rich in medium length chain TAG species like CN38:0 and CN40:1, whereas stearin was rich in saturated long chain TAG species from CN42:0 to CN52:0. Separation of the TAGs based on saturation degree allowed successful selection of the TAG parent-ion for fragmentation by eliminating the interferences of TAG species that have the same carbon number but vary in number of double bonds. The TAG fragmentation patterns indicated significant differences between AMF, olein and stearin as a result of the dry fractionation process. Compared to AMF, olein yielded in higher fragments of short-chain saturated and middle-chain unsaturated FAs. Whereas, stearin yielded in saturated and monounsaturated long chain FA fragments. Fragmentation of unsaturated long chain TAGs showed that the TAGs in olein contained more C18:1 and C18:2 than that of AMF and stearin. Stearin on the other hand, contained higher amount of TAG species containing C16:0. These results were in line with the FA compositions obtained from GC-FID and suggest that Ag⁺-SPE cartridges coupled with MALDI-TOF-MS offer an informative and practical approach to characterise fats and oils with complex TAG composition.

Triglyceride, fatty acid profile and antioxidant characteristics of low melting point fractions of Buffalo Milk fat

BACKGROUND

Among the dietary lipids, milk fat is most complicated as it contains more than one hundred types of fatty acids and several triglycerides. Huge versatility in triglyceride and fatty composition makes it possible to convert milk fat into various fractions on the basis of melting characteristics. Functional properties of milk fat can be increased by converting it into different fractions. After cow milk, buffalo milk is the second largest source of milk and chemical characteristics of buffalo milk fat has been studied in a limited fashion. The main mandate was determination of triglyceride, fatty acid profile and antioxidant characteristics of low melting point fractions of buffalo milk fat for increased industrial applications.

METHODS

Buffalo milk fat (cream) was fractionated at three different temperatures i.e. 25, 15 and 10 °C by dry fractionation technique and packaged in 250 ml amber glass bottles and stored at ambient temperature for 90 days. The fraction of milk fat harvested at 25, 15 and 10 °C were declared as LMPF-25, LMPF-15 and LMPF-10. Unmodified milk fat was used as control (PBMF). Low melting point fractions were analyzed for triglyceride composition, fatty acid profile, total phenolic contents, DPPH free radicals scavenging activity, reducing power, free fatty acids, peroxide value, iodine value and conjugated dienes at 0, 45 and 90 days of storage.

RESULTS

In LMPF-10, concentrations of C₃₆, C₃₈, C₄₀, and C₄₂ were 2.58, 3.68, 6.49 and 3.85% lower than PBMF. In LMPF-25, concentrations of C₄₄, C₄₆, C₄₈, C₅₀, C₅₂ and C₅₄ were 0.71, 1.15, 2.53, 4.8, 0.39 and 2.39% higher than PBMF. In LMPF-15, concentrations of C₄₄, C₄₆, C₄₈, C₅₀, C₅₂ and C₅₄ were 2.45, 4.2, 3.47, 5.92, 2.38 and 3.16% higher than PBMF. In LMPF-10, concentrations of C₄₄, C₄₆, C₄₈, C₅₀, C₅₂ and C₅₄ were 2.8, 5.6, 5.37, 7.81, 3.81 and 4.45% higher than PBMF. LMPF-25, LMPF-15 and LMPF-10 had higher concentration of unsaturated fatty acids as compared PBMF. Total phenolic contents of buffalo milk fat and its fractions were in the order of LMPF-10 > LMPF-15, LMPF-25 > PBMF. Storage period of 45 days had a non-significant effect on total flavonoid content. 2, 2-Diphenyl-1-picrylhydrazyl free radical scavenging activity (DPPH) free radical scavenging activity of LMP-25, LMPF-15 and LMPF-10 were 4.8, 13.11 and 25.79% higher than PBMF. Reducing power of PBMF, LMPF-25, LMPF-15 and LMPF-10 were 22.81, 28.47, 37.51 and 48.14, respectively. Estimation of free fatty acids after the 90 days of storage duration, no significant difference was found in content of free fatty acids in unmodified milk fat and low melting point fractions. Testing of peroxide value in 90 days old samples showed that peroxide value of PBMF, LMPF-25, LMPF-15 and LMPF-10 was 0.54, 0.98, 1.46 and 2.22 (MeqO₂/kg), respectively. Storage period up to 45 days had a non-significant effect on anisidine value, iodine value and conjugated dienes.

CONCLUSION

Low melting point fractions of buffalo milk fat had higher concentration of unsaturated fatty acids and more antioxidant capacity than unmodified milk fat with reasonable storage stability.

Effect of calcium on fatty acid bioaccessibility during in vitro digestion of Cheddar-type cheeses prepared with different milk fat fractions

Calcium plays an important role in intestinal lipid digestion by increasing the lipolysis rate, but also limits fatty acid bioaccessibility by producing insoluble Ca soaps with long-chain fatty acids at intestinal pH conditions. The aim of this study was to better understand the effect of Ca on the bioaccessibility of milk fat from Cheddar-type cheeses. Three anhydrous milk fats (AMF) with different fatty acid profiles (olein, stearin, or control AMF) were used to prepare Cheddar-type cheeses, which were then enriched or not with Ca using CaCl₂ during the salting step. The cheeses were digested in vitro, and their disintegration and lipolysis rates were monitored during the process. At the end of digestion, lipids were extracted under neutral and acidic pH conditions to compare free fatty acids under intestinal conditions in relation to total fatty acids released during the digestion process. The cheeses prepared with the stearin (the AMF with the highest ratio of long-chain fatty acids) were more resistant to disintegration than the other cheeses, owing to the high melting temperature of that AMF. The Ca-enriched cheeses had faster lipolysis rates than the regular Ca cheeses. Chromatographic analysis of the digestion products showed that Ca interacted with long-chain fatty acids, producing Ca soaps, whereas no interaction with shorter fatty acids was detected. Although higher Ca levels resulted in faster lipolysis rates, driven by the depletion of reaction products as Ca soaps, such insoluble compounds are expected to reduce the bioavailability of fatty acids by hindering their absorption. These effects on lipid digestion and absorption are of interest for the design of food matrices for the controlled release of fat-soluble nutrients or bioactive molecules.

Effect of Phytosterols on the Crystallization Behavior of Oil-in-Water Milk Fat Emulsions

Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.

Rice oil as a green source of capping ligands for GdF3 nanocrystals

The thermal decomposition of triglycerides allows control of the amount of ligands in the synthesis of GdF₃ nanocrystals.

Crystallization and polymorphism of triacylglycerols contribute to the rheological properties of processed cheese

The thermal, rheological, and structural behaviors of a spreadable processed cheese were studied by complementary techniques including differential scanning calorimetry (DSC), rheology, and X-ray diffraction as a function of temperature. In this product, fat is present as a dispersed phase. Thermal and rheological properties were studied at different cooling rates between 0.5 and 10 degrees C min(-1) from 60 to 3 degrees C. Crystallization properties of fat were monitored at a cooling rate of -2 degrees C min(-1) from 60 to -10 degrees C. Fat triacylglycerols (TGs) crystallized at 15 degrees C in a triple-chain length 3Lalpha (72 A) structure correlated to exothermic events and to the sudden increase in the rheological moduli G' and G''. Upon heating at 2 degrees C min(-1), the polymorphic transition of TGs evidence the melting of the 3Lalpha structure and the formation of a 2Lbeta' (36.7-41.5 A) structure. Melting of the latter follows. These transformations coincide with thermal events observed by DSC and the decrease in two steps of the rheological moduli. The influence of fat crystallization, melting, and polymorphism upon the viscoelastic properties is clearly demonstrated upon both heating and cooling.

Triglycerides obtained by dry fractionation of milk fat: 2. Thermal properties and polymorphic evolutions on heating

The crystallographic and thermal properties of milk fat and fractions were investigated on heating using the coupling of synchrotron X-ray diffraction with differential scanning calorimetry. We showed that re-crystallisations occurred during the heating of the stearin and the olein fractions with the formation of a beta' 2L (41.1-42.6A) structure and a beta' 3L (66A) structure, respectively. By creating a quantified solid-liquid phase behaviour versus temperature diagram, the amount of the solid and liquid phases and the relative proportion of each of the crystalline structures within the solid phase were determined.

Crystallization properties and polymorphism of triacylglycerols in goat's milk fat globules

The sensorial, functional, and nutritional properties of goat dairy products result from the specific fatty acid composition of goat's milk fat. However, information on the physical and thermal properties of goat's milk fat is scarce. In this study, crystallization of triacylglycerols (TG) in goat's milk fat globules was investigated using polarized light microscopy and the coupling of time-resolved synchrotron radiation X-ray diffraction (XRD) and high-sensitivity differential scanning calorimetry (DSC). The molecular organization of the solid fat phase was characterized for cooling rates between 3 and 0.1 degrees C/min. Quenching of goat's milk fat globules from 50 to -8 degrees C and 4 degrees C was also examined to identify the most unstable polymorphic forms of TG. Then, the melting behavior of fat crystals was studied on subsequent heating at 1 degrees C/min. Triple chain length (3L: 68.6-70 A) and double chain length (2L: 37-45.4 A) structures were characterized and 5 polymorphic forms, alpha, sub-alpha, beta' 1, beta' 2, and beta were identified. Polymorphic transitions were observed within goat's milk fat globules as a function of time after quenching and as a function of temperature on heating. From a technological point of view, this work will contribute to a better understanding of the rheological properties as well as on the flavor evolutions of goat's milk-based products.

Natural wax constituents of a supercritical fluid CO(2) extract from quince (Cydonia oblonga Mill.) pomace

The chemical constituents of a lipophilic extract from quince (Cydonia oblonga Mill.), obtained by supercritical fluid CO(2) extraction of the dried fruit pomace were investigated. Solvent partition of quince wax with n-hexane or acetone yielded an insoluble (crystalline) and a soluble (oily) fraction. Both fractions were analyzed separately using gas chromatography/mass spectrometry (GC/MS). The insoluble fraction consisted of saturated n-aldehydes, n-alcohols and free n-alkanoic acids of carbon chain lengths between 22 and 32, with carbon chain lengths of 26 and 28 dominating. Also odd-numbered unbranched hydrocarbons, mainly C27, C29 and C31, were detected particularly in the acetone-insoluble fraction (total, 15.8%). By means of vacuum liquid chromatography, triterpenoic acids were separated from the hexane-insoluble matter and identified as a mixture of ursolic, oleanolic and betulinic acids. The major constituents of the hexane-soluble fraction were glycerides of linoleic [Δ(9,12), 18:2] and oleic [Δ(9), 18:1] acids, accompanied by free linoleic, oleic and palmitic acids (C16). Moreover β-sitosterol, Δ(5)-avenasterol as well as trace amounts of other sterols were assigned. Finally the carotenoids phytoene and phytofluene were identified and quantified by UV/vis and high-performance liquid chromatography/MS techniques, yielding 1.0 and 0.3% of the quince wax, respectively. It is anticipated that the complex of lipid constituents from quince wax may exert interesting biological activities, the elucidation of which awaits further studies.

Multiscale characterization of the organization of triglycerides and phospholipids in emmental cheese: from the microscopic to the molecular level

The chemical composition and properties of lipids, both triglycerides and phospholipids, play a major role in the functional and nutritional properties of food products. In this study, the suprastructure of fat, solid fat content, and crystallographic properties of triglycerides were investigated in hard-type cheeses from the microscopic scale to the molecular level using the combination of relevant techniques. Two industrial cheeses with different oiling off properties were compared with experimental cheeses manufactured in the laboratory. Microstructural analysis performed using confocal laser scanning microscopy showed that milk processing led to the disruption of fat globules with the formation of nonglobular fat. For a similar fatty acid composition, oiling off was mainly related to the fat in dry matter content and to the suprastructure of fat in cheese. An exogenous fluorescent phospholipid permitted the localization of milk phospholipids in the cheese matrix, which mainly remain around fat inclusions after disruption of the milk fat globule membrane, and to show heterogeneities. We also showed using differential scanning calorimetry that the suprastructure of fat did not affect the solid fat content in cheese at 4 degrees C: 71.6 +/- 4.9%. The organization of triglyceride molecules in fat crystals, elucidated at a molecular level using X-ray diffraction, corresponded to the coexistence of 2 lamellar structures (2L 40.5 angstroms and 3L 54.6 angstroms) with four polymorphic forms: alpha, two beta' and beta. A schematic representation of the multiscale organization of triglycerides and phospholipids in cheese is proposed.

Liposomal formulation of a glycerolipidic prodrug for lymphatic delivery of didanosine via oral route

Didanosine is a polar drug with poor membrane absorption and high hepatic first pass metabolism. This study aimed at developing a lipidic formulation of a glycerolipidic prodrug of didanosine in order to improve its bioavailability. In the course of a preformulation study, the glycerolipidic prodrug of didanosine was characterized by microscopy, DSC and XRDT. In anhydrous conditions, the prodrug displayed a polymorphic behaviour similar to that of triglycerides. Then, we evaluated three types of lipidic formulations (emulsions, mixed micelles and liposomes) in order to encapsulate the prodrug. Solubilities in water - even in the presence of taurocholate micelles - but also in some oils were very low (max 244 microg/mL) as the prodrug was found to be amphiphilic (log P=2). On the contrary, the prodrug was found to be perfectly incorporated in dipalmitoylphosphatidylcholine (DPPC) multilamellar liposomes up to a ratio of 1:5 (mol:mol) prodrug:DPPC as suggested by HPLC-UV and DSC experiments. Moreover, these liposomes could be freeze-dried whereas the chemical integrity of the prodrug was preserved. Then, the freeze-dried liposomal preparation could be formulated as gastro-resistant capsules to prevent didanosine from acidic degradation. Further experiments are on the way to evaluate in vitro the absorption of prodrug incorporated in liposomes by enterocytes.